# If #"NaCl"# is dissolved in water to raise its boiling point by #2.10^@ "C"#, what is the molarity? #K_b = 0.512^@ "C/m"#.

##### 1 Answer

Jun 28, 2017

I assume you mean molality.

The **boiling point elevation**

#DeltaT_b = T_b - T_b^"*" = iK_bm#

The van't Hoff factor for **molality** is:

#DeltaT_b = 102.10^@ "C" - 100.00^@ "C" = (2)(0.512^@ "C"cdot"kg/mol")m#

#=>m = (2.10cancel(""^@ "C"))/(2 cdot 0.512cancel(""^@ "C")cdot"kg/mol")#

#=>color(blue)(m = "2.051 mol solute/kg solvent")#

If you want the molarity, you'll have to provide the new volume of the solution.